How AT&T and T-Mobile are ripping off their prepaid customers

Federal regulators may have approved AT&T's bid to merge with Leap Wireless, aka Cricket -- a deal that will add 5 million customers to AT&T's rolls.

But fans of Cricket's service may have a reason to be wary of their new corporate overlords. That's because prepaid customers on AT&T are routinely being billed extra for minutes they don't appear to be using. If true, that means their available credit is being drained at unexpected rates -- often without their knowledge -- requiring that they buy more credit, more often.

Critics allege the practice amounts to a subtle program of consumer fraud that, in the aggregate, delivers big bucks to wireless carriers. According to a formal complaint lodged with federal regulators, wireless companies are reporting longer call times than what a customer's device will show. In the case of one AT&T subscriber, the network added as many as 33 seconds to his call after he hung up, allowing AT&T to bill him for an additional minute of usage.